Why do people who are about to die look perfectly healthy just hours before

Death is, without a doubt, one of the hardest parts of human life. To see a loved one breathe their last, or just seeing someone leave their body behind, is traumatic to say the least. And even for the person who is dying, it is a whirlwind of emotions. Death comes slowly, especially in the case of long illnesses, and brings with it pain, helplessness, and emotional suffering for the dying person and their loved ones.
But sometimes, something unexpected happens in the final hours or days before death. A person who has been unconscious, confused, or barely living. suddenly becomes alert, talkative, or even joyful.

As the end nears, suffering comes in many forms, and not all of it is emotional. While people try to heal the sick, deceased person externally, with medicines, therapies, and more, the brain too works in a certain way, trying to avoid death. People nearing death feel fear, sadness, and a deep sense of detachment from their body and mind.
And in these situations, ‘Terminal Lucidity’ hits the internal system.

Terminal lucidity is the sudden return of mental clarity and awareness shortly before death in a person who was severely ill for the last couple months and days. This happens sometimes hours or even days before death, and the person becomes hyperactive, performing tasks, speaking clearly, recognising and meeting all their family members, hanging out with them, and much more.

Terminal lucidity does not have a full and final answer, but there are numerous assumptions and arguments as to how it works.
It is said that as the body shuts down, chemicals in the brain and body are subject to change. And so some researchers believe that there is a temporary spike in neurotransmitters that ‘light up' certain parts of the brain, which makes the person fully aware and active of the things around them.
Some also say that in the final moments the body goes into a survival mode of sorts, activating a temporary wakefulness that makes people extra active and agile just before it realises that it can’t function anymore.

People who experience this, as survivors of the deceased person, just like to believe that it is a final gift from God. After days, weeks, or even months of silence, seeing a loved one smile, speak, or say goodbye is extremely emotional, gives them closure, and there is no final guilt in them that they weren’t able to properly say goodbye.
And so they see it as God's way of easing the pain with a last conversation or a moment of connection, before the soul passes on.

Some also say and believe that terminal lucidity is a sign of the body’s or soul’s will to hold on, even if briefly. This theory suggests that the dying person, deep down, wants to try their best to give life another shot, and thus their body and mind pushes through the illness, giving them some moments of happiness.